Listen on the group socket and handle requests

src/common/serialization.cpp

@@ -108,3 +108,7 @@ AEffect& update_aeffect(AEffect& plugin, const AEffect& updated_plugin) {
 
     return plugin;
 }
+
+bool PluginParameters::operator==(const PluginParameters& rhs) const {
+    return plugin_path == rhs.plugin_path && socket_path == rhs.socket_path;
+}

src/common/serialization.h

@@ -571,3 +571,30 @@ struct AudioBuffers {
         s.value4b(sample_frames);
     }
 };
+
+/**
+ * An object containing the startup options for hosting a plugin in a plugin
+ * group process. These are the exact same options that would have been passed
+ * to `yabridge-host.exe` were the plugin to be hosted individually.
+ */
+struct PluginParameters {
+    std::string plugin_path;
+    std::string socket_path;
+
+    bool operator==(const PluginParameters& rhs) const;
+
+    template <typename S>
+    void serialize(S& s) {
+        s.text1b(plugin_path, 4096);
+        s.text1b(socket_path, 4096);
+    }
+};
+
+template <>
+struct std::hash<PluginParameters> {
+    std::size_t operator()(PluginParameters const& params) const noexcept {
+        std::hash<string> hasher{};
+
+        return hasher(params.plugin_path) ^ (hasher(params.socket_path) << 1);
+    }
+};

src/plugin/plugin-bridge.cpp

@@ -121,7 +121,12 @@ PluginBridge::PluginBridge(audioMasterCallback host_callback)
     std::thread([&]() {
         using namespace std::literals::chrono_literals;
 
-        // TODO: Figure out how this check would work with plugin gruops
+        // TODO: For plugin groups, we should be polling whether someone is
+        //       still listening on the group socket (and ideally we should be
+        //       able to tell it's the same process). If we can't figure out a
+        //       better way, then we could just return the PID when sending the
+        //       host request to the group process and check whether that
+        //       process is still running.
         while (true) {
             if (finished_accepting_sockets) {
                 return;

src/wine-host/bridges/group.cpp

@@ -20,6 +20,8 @@
 #include <boost/asio/read_until.hpp>
 #include <regex>
 
+#include "../../common/communication.h"
+
 // FIXME: `std::filesystem` is broken in wineg++, at least under Wine 5.8. Any
 //        path operation will thrown an encoding related error
 namespace fs = boost::filesystem;
@@ -29,6 +31,13 @@ namespace fs = boost::filesystem;
  */
 std::string create_logger_prefix(const fs::path& socket_path);
 
+// CreateThread() is great and allows you to pass a single value to the
+// function, so we'll use this to pass both `this` and the parameters to the
+// below thread function so it can do its thing.
+using handle_host_plugin_parameters = std::pair<GroupBridge*, PluginParameters>;
+
+uint32_t WINAPI handle_host_plugin_proxy(void* param);
+
 StdIoCapture::StdIoCapture(boost::asio::io_context& io_context,
                            int file_descriptor)
     : pipe(io_context),
@@ -54,10 +63,6 @@ StdIoCapture::~StdIoCapture() {
     close(pipe_fd[0]);
 }
 
-bool PluginParameters::operator==(const PluginParameters& other) const {
-    return removeme == other.removeme;
-}
-
 GroupBridge::GroupBridge(boost::filesystem::path group_socket_path)
     : logger(Logger::create_from_environment(
           create_logger_prefix(group_socket_path))),
@@ -77,18 +82,58 @@ GroupBridge::GroupBridge(boost::filesystem::path group_socket_path)
 }
 
 void GroupBridge::handle_host_plugin(const PluginParameters& parameters) {
-    // TODO: Start the plugin,
+    // TODO: Start the plugin
     // TODO: Allow this process to exit when the last plugin exits. Make sure
     //       that that doesn't cause any race conditions.
 }
 
 void GroupBridge::handle_incoming_connections() {
-    // TODO: Accept connections here
+    accept_requests();
 
     logger.log("Now accepting incoming connections");
     io_context.run();
 }
 
+void GroupBridge::accept_requests() {
+    group_socket_acceptor.async_accept(
+        [&](const boost::system::error_code& error,
+            boost::asio::local::stream_protocol::socket socket) {
+            // Stop the whole process when the socket gets closed unexpectedly
+            if (error.failed()) {
+                logger.log("Error while listening for incoming connections:");
+                logger.log(error.message());
+
+                io_context.stop();
+            }
+
+            // Read the parameters, and then host the plugin in this process
+            // just like if we would be hosting the plugin individually through
+            // `yabridge-hsot.exe`. Since we're using sockets there's no reason
+            // to send an acknowledgement back. One potential issue here is that
+            // it will be hard to tell whether a plugin has crashed before
+            // initialization, and that the sockets will never be accepted. For
+            // individually hosted plugins we poll whether the Wine process is
+            // still active so we can terminate early if it is not, but in this
+            // case the yabridge instance has to determine that this process is
+            // still running.
+            const auto parameters = read_object<PluginParameters>(socket);
+
+            // Collisions in the generated socket names should be very rare, but
+            // it could in theory happen
+            std::lock_guard lock(active_plugins_mutex);
+            assert(active_plugins.find(parameters) != active_plugins.end());
+
+            // CreateThread() doesn't support multiple arguments and requires
+            // manualy memory management.
+            handle_host_plugin_parameters* thread_params =
+                new std::pair<GroupBridge*, PluginParameters>(this, parameters);
+            active_plugins[parameters] =
+                Win32Thread(handle_host_plugin_proxy, &thread_params);
+
+            accept_requests();
+        });
+}
+
 void GroupBridge::async_log_pipe_lines(
     boost::asio::posix::stream_descriptor& pipe,
     boost::asio::streambuf& buffer,
@@ -135,3 +180,16 @@ std::string create_logger_prefix(const fs::path& socket_path) {
 
     return "[" + socket_name + "] ";
 }
+
+uint32_t WINAPI handle_host_plugin_proxy(void* param) {
+    // The Win32 API only allows you to pass a void pointer to threads, so we
+    // need to use manual memory management.
+    auto thread_params = static_cast<handle_host_plugin_parameters*>(param);
+    GroupBridge* instance = thread_params->first;
+    PluginParameters& parameters = thread_params->second;
+    delete thread_params;
+
+    instance->handle_host_plugin(parameters);
+
+    return 0;
+}

src/wine-host/bridges/group.h

@@ -24,21 +24,6 @@
 
 #include "vst2.h"
 
-// TODO: Replace this with a proper struct that contains the required arguments
-//       for creating a PluginBridge instance
-struct PluginParameters {
-    int removeme;
-
-    bool operator==(const PluginParameters& p) const;
-};
-
-template <>
-struct std::hash<PluginParameters> {
-    std::size_t operator()(PluginParameters const& params) const noexcept {
-        return std::hash<int>{}(params.removeme);
-    }
-};
-
 /**
  * Encapsulate capturing the STDOUT or STDERR stream by opening a pipe and
  * reopening the passed file descriptor as one of the ends of the newly opened
@@ -123,6 +108,8 @@ class GroupBridge {
      *   where `<wine_prefix_id>` is a numerical hash as explained in the
      *   `create_logger_prefix()` function in `./group.cpp`.
      *
+     * @throw boost::system::system_error If we can't listen on the socket.
+     *
      * @note Creating an `GroupBridge` instance has the side effect that the
      *   STDOUT and STDERR streams of the current process will be redirected to
      *   a pipe so they can be properly written to a log file.
@@ -132,10 +119,10 @@ class GroupBridge {
     /**
      * Host a new plugin within this process. Called by proxy using
      * `handle_host_plugin_proxy()` in `./group.cpp` because the Win32
-     * `CreateThread` API only allows passing a single pointer to the function.
-     * Because we don't have access to our own thread handle, the thread that's
-     * listening on the group socket and that has created this thread will also
-     * add this thread to the `active_plugins` map.
+     * `CreateThread` API only allows passing a single pointer to the function
+     * and does not allow lambdas. Because we don't have access to our own
+     * thread handle, the thread that's listening on the group socket will have
+     * already added this thread to the `active_plugins` map.
      *
      * Once the plugin has exited, this thread will then remove itself from the
      * `active_plugins` map. If this causes the vector to become empty, we will
@@ -158,6 +145,17 @@ class GroupBridge {
     void handle_incoming_connections();
 
    private:
+    /**
+     * Listen on the group socket for incoming requests to host a new plugin
+     * within this group process. This will asynchronously listen on the socket,
+     * and for any connection made it will retrieve a `PluginParameters` object
+     * containing information about the plugin to host and then spawn a new
+     * thread to start hosting that plugin.
+     *
+     * @see handle_host_plugin
+     */
+    void accept_requests();
+
     /**
      * Continuously read from a pipe and write the output to the log file. Used
      * with the IO streams captured by `stdout_redirect` and `stderr_redirect`.
@@ -206,11 +204,11 @@ class GroupBridge {
     /**
      * A map of threads that are currently hosting a plugin within this process.
      * After a plugin has exited or its initialization has failed, the thread
-     * handling it will remove itself from this map.
+     * handling it will remove itself from this map. This is to keep track of
+     * the amount of plugins currently running with their associated thread
+     * handles.
      */
-    std::unordered_map<PluginParameters,
-                       std::pair<Win32Thread, std::unique_ptr<Vst2Bridge>>>
-        active_plugins;
+    std::unordered_map<PluginParameters, Win32Thread> active_plugins;
     /**
      * A mutex to prevent two threads from simultaneously accessing the plugins
      * map, and also to prevent `handle_host_plugin()` from terminating the

src/wine-host/group-host.cpp

@@ -56,31 +56,29 @@ int __cdecl main(int argc, char* argv[]) {
 
     const std::string group_socket_endpoint_path(argv[1]);
 
-    // TODO: Catch exception during initialization when another process is
-    //       already listening on the socket. Make sure to print a more useful
-    //       message instead.
-    try {
-        std::cerr << "Initializing yabridge group host version "
-                  << yabridge_git_version
+    std::cerr << "Initializing yabridge group host version "
+              << yabridge_git_version
 #ifdef __i386__
-                  << " (32-bit compatibility mode)"
+              << " (32-bit compatibility mode)"
 #endif
-                  << std::endl;
+              << std::endl;
 
+    try {
         GroupBridge bridge(group_socket_endpoint_path);
 
         // Blocks the main thread until all plugins have exited
         bridge.handle_incoming_connections();
-    } catch (const std::runtime_error& error) {
-        // Even though the process will likely outlive the yabridge instance
-        // that spawns it, we can still print any initialization messages and
-        // errors to STDERR since at this point there will still be a yabridge
-        // instance capturing this process's output.
+    } catch (const boost::system::system_error& error) {
+        // If another process is already listening on the socket, we'll just
+        // print a message and exit quietly. This could happen if the host
+        // starts multiple yabridge instances that all use the same plugin group
+        // at the same time.
         // TODO: Check if this is printed on the right stream
-        std::cerr << "Error while initializing the group host process:"
+        std::cerr << "Another process is already listening on this group's "
+                     "socket, connecting to the existing process:"
                   << std::endl;
         std::cerr << error.what() << std::endl;
 
-        return 1;
+        return 0;
     }
 }

src/wine-host/individual-host.cpp

@@ -54,6 +54,7 @@ int __cdecl main(int argc, char* argv[]) {
               << " (32-bit compatibility mode)"
 #endif
               << std::endl;
+
     try {
         Vst2Bridge bridge(plugin_dll_path, socket_endpoint_path);
         std::cerr << "Finished initializing '" << plugin_dll_path << "'"